Studies will be continued on a project dealing with Siphonaptera (fleas) and which contribute to the prevention and control of ectoparasite-borne diseases by the following means: 1) in investigations on medical ecology, obtain and interpret data on faunal relations and zoogeography of fleas and their hosts, and thereby be able to make valid predictions about the geographical and topographical distribution of such infections, even in the absence of human cases. 2) Learn as much as possible about certain major groups of fleas which are actual or potential vectors of disease, including the study of such subjects as the interrelations between fleas and their hosts; the adaptations of fleas for a parasitic existence; their evolution; their distribution and that of their hosts; seasonal abundance, etc. 3) Clarify the taxonomy of these Siphonapters so as to permit the prompt and accurate identification of potential vectors, especially rodent-fleas, by preparing generic revisions, including illustrations of known species and keys to facilitate their precise determination, and by describing new genera and species, or diagnosing little-known taxa in selected groups of Siphonaptera. The main area under study include Ethiopia, Pakistan, Iran, the Indo-Malayan region, the Philippines, Indonesia, Australia, New Guinea, Mexico and Central America. The specimens of fleas and other ectoparasites used in these studies have been (or are being) collected by the field teams of this Department while engaged in investigations of viral and rickettsial diseases under non-Grant sponsorship, or by other institutions engaged in field work in these areas. The specimens of fleas are prepared for study and are identified in our laboratory, and these methods, and the analyses of the data, are standard and based upon our past experience.